The present invention relates to a field-effect mode liquid crystal display and, more particularly, to a field-effect mode liquid crystal display which can display colored images.
In the conventional field-effect mode liquid crystal display, a liquid crystal cell containing a liquid crystal composition having positive dielectric anisotropy characteristics, is placed between cross-polarizers, whereby the unactivated cell can be made to transmit light. When a liquid crystal display cell of this type is activated by applying a potential thereacross, the ability of the liquid crystal to rotate the plane of polarization is destroyed and the cell appears dark or opaque since the incident light is blocked by the analyzer.
On the other hand, the display can be constructed so as to normally block light until activated. The result is essentially the same except that images appear white on a black background rather than vice versa as is the case when the display transmits light when unactivated.
When polarizers accompany a color filtering characteristic, a colored image appears on the above-mentioned field-effect mode liquid crystal display. However, the image is colored only on its clear portion and the black portion still remains black. Moreover, the images are colored in a predetermined color, and multicolored images can not be obtained.
Accordingly, an object of the present invention is to provide a field-effect mode liquid crystal display which can produce colored images.
Another object of the present invention is to provide a field-effect mode liquid crystal display wherein images appear in one color on a complementary color background.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objectives, pursuant to an embodiment of the present invention, a retardation plate is placed between a liquid crystal display cell containing a liquid crystal composition having positive dielectric anisotropy characteristics and one of a pair of polarizers. The retardation plate creates phase differences of discriminative degrees in dependence on the differences of the wave length of the light passing therethrough. With such an arrangement, the images appear in one color on the complementary color background.
In a preferred form, the retardation plate is corrugated, thereby displaying images in a plurality of pairs of complementary colors.